Low Temperature Si/SiOx/pc-Si Passivated Contacts to n-Type Si Solar Cells

We describe the design, fabrication, and results of low-recombination, passivated contacts to n-type silicon utilizing thin SiOx, and plasma enhanced chemical vapor deposited doped polycrystalline-silicon (pc-Si) layers. A low-temperature silicon dioxide layer is grown on both surfaces of an n-type CZ wafer to a thickness of < 20 angstrom. Next, a thin layer of P-doped plasma enhanced chemical vapor deposited amorphous silicon (n/a-Si:H) is deposited on top of the SiOx. The layers are annealed to crystallize the a-Si:H and diffuse H to the Si/SiOx interface, after which a metal contacting layer is deposited over the conducting pc-Si layer. The contacts are characterized by measuring the recombination current parameter of the full-area contact (J(o,contact)) to quantify the passivation quality, and the specific contact resistivity (rho(contact)). The Si/SiOx/pc-Si contact has an excellent J(o,contact) = 3 0 fA/cm(2) and a good rho(contact) = 29.5 mOhm-cm(2). Separate processing conditions lowered J(o,contact) to 12 fA/cm(2). However, the final metallization can substantially degrade this contact and has to be carefully engineered. This contact could be easily incorporated into modern, high-efficiency solar cell designs, benefiting performance and yet simplifying processing by lowering the temperature and growth on only one side of the wafer.